Manchester United have agreed to sign Argentina central defender Lisandro Martinez from Ajax in a deal worth up to 67m euros (£57m). Starnews Reports   The 24-year-old is expected to sign a five-year contract with the option of a further year.     The move, for an initial £49m, is subject to a medical, personal terms being finalised and a UK visa.   The deal includes £8.5m in add-ons and £2.2m in solidarity payments to Martinez's former clubs.   Martinez: Who is Man Utd's new 'Butcher of Amsterdam'? He made 120 appearances for Ajax after moving from Argentinian